The present invention relates to an apparatus and a method of screen printing, which is a way of printing paste, e.g. creamy solder paste and conductive paste, on a substrate.
Screen-printing method has been used for printing paste, e.g., creamy solder paste, on a substrate. This method includes the following steps:
(a) Attaching a screen mask, which has pattern openings formed therein corresponding to positions to be printed on the substrate, onto the substrate; and
(b) Supplying creamy solder paste onto the mask and sliding squeegees. Solder paste is printed on the substrate through the pattern openings.
After the above steps finish, printing inspection for inspecting the state of creamy solder paste printed on the substrate is performed. A screen-printing apparatus equipped with print-checking capability is widely known that printing inspection is performed in the apparatus. Conventionally, such an apparatus with inspecting capability takes an image of the substrate by a camera mounted for recognizing a printed substrate, performs the image processing and determines whether or not the creamy solder paste is printed precisely on a position to be printed.
In this kind of screen printing, to ensure good-quality printing requires to set proper printing conditions responsive to each object to be printed. Various parameters, e.g. the velocity at which squeegees are slid on the mask in screen printing, the printing pressure at which the squeegees are pressed against the mask and a substrate-detaching velocity relative to the mask. These various parameters are predetermined responsive to features of each object. This operation of setting these conditions has been adjusted by skilled labor having extensive experience.
This kind of screen printing apparatuses include moving mechanisms performing predetermined movements for each printing operation, e.g. a substrate-positioning section for holding and positioning the substrate or a mechanism for raising and lowering the substrate toward or away from relatively to the mask. A control mechanism being capable of controlling positions with numeric data, e.g. servomechanism, is used in these moving mechanisms. To ensure good positioning accuracy in the control mechanism requires a teaching operation in order to preset a parameter indicating the position of the origin in a control program responsive to an origin of a mechanical-coordinate system in an actual apparatus. Generally, the teaching operation has been manually performed by a skilled person using various measuring instruments when he or she activates the apparatus or carries out a regular maintenance.
The forgoing conventional screen-printing apparatus has problem as described below.
First, a conventional printing inspection has used a method of determining on the basis of two-dimensional image data taken by the camera mounted in the apparatus. Therefore, when an inspection item can be determined by only two-dimensional data, e.g. printing position, plane shape, high-quality results are obtained. However, when an inspection item needs three-dimensional data for pass/fail determination, e.g. the amount of printing, height of printing, highly-accurate inspection by the conventional method has been impossible. Additionally, after screen printing is completed, the printed substrate is conventionally inspected by camera, and only the printing results for pass/fail determination are obtained. However, data enough to identify the causes of print failure cannot be obtained. To address the problem of print failure has been difficult due to data shortages.
Second, a number of skilled labor has declined year and year. To gather skilled labor for setting printing conditions has been difficult. Moreover, a manufacturing system shifts to a flexible manufacturing system, i.e., limited production of a variety products. Every time a kind of product is changed, printing conditions has to be changed. Therefore, an immatured-skilled person is obliged to set the printing condition. As a result, the printing conditions are varied depending on the difference of the experiences. Consequently, in the conventional screen printing, to keep stable-high-quality printing has been difficult due to variation of printing conditions.
Third, machine adjusting operation or teaching operation in the conventional manner needs adjustment operation such as measurement of relative position in each section of the machine. Therefore, the operation becomes complicated and teaching operation has taken time and labor. A method that can carry out adjustment of mechanisms and teaching operations with ease and accuracy has been required.
The present invention addresses the problems discussed above, and aims to provide an apparatus and a method of screen printing having various advantages as shown below.
(a) The apparatus can carry out printing inspection with high accuracy by three-dimensional measuring means.
(b) The apparatus can provide data to identify the cause of the print failure, consequently, it prevents the print failure from occurring.
(c) The apparatus can set printing conditions with ease and without disperses of the printing conditions, and this allows good quality of printing.
(d) The apparatus can carry out adjustment of mechanisms and teaching operations with ease and high accuracy.
The apparatus of the present invention prints a pattern with pastes on a substrate via pattern openings by attaching a screen mask onto the substrate and sliding a squeegee head on the screen mask. The apparatus includes the following elements.
(a) A substrate-positioning means for precisely positioning the substrate relatively to the screen mask having pattern openings;
(b) A three-dimensionally-measuring means for three-dimensionally measuring the top surface of the screen mask at a position to be printed and a top of the substrate at a position to be measured;
(c) A transfer means for moving the three-dimensionally measuring means; and
(d) An inspecting means for inspecting at least one of the substrate or the screen mask based on results measured by the three-dimensional measuring means.
The method of screen printing of the present invention includes the following steps.
(a) Substrate-positioning process for positioning the substrate relative to the screen mask;
(b) Three-dimensional measuring process for measuring three-dimensionally the top surface of the screen mask at a position to be printed and the top surface of the substrate at a substrate-measuring position; and
(c) Inspection process for inspecting at least one of the substrate or the screen mask by an inspecting means based on the measuring result by the three-dimensional measuring means.
This configuration or this method allows the substrate and the screen mask to be inspected before and after screen printing, and the causes of the failures to be identified with ease.
Another screen-printing apparatus of the present invention includes the following elements.
(a) A substrate-positioning means for positioning the substrate relative to the screen mark having pattern openings;
(b) A three-dimensional measuring means for measuring screen mask from the above at a printing position and the substrate at the substrate-measuring positioning position;
(c) A moving means for moving the three-dimensional measuring means;
(d) A printing-condition-setting means for setting screen-printing condition based on measuring results by the three dimensional measuring; and
(e) A printing-condition storing means;
Another method of screen printing of the present invention includes the following steps.
(a) After printing measurement-process for measuring at least one of the screen mask at printing position and the substrate at the substrate measuring position from the above;
(b) A printing-conditions-setting process for setting screen-printing condition; and
(c) A storing process for storing the printing condition set in a print-condition-storing means.
According to this configuration or this method, the substrate and the screen mask after screen printing are measured from the above by the three-dimensional measuring means and by setting conditions of screen printing based on the measuring results. This allows disperses in setting conditions of printing to be eliminated and stable good printing quality to be ensured.
Further another screen-printing apparatus of the present invention includes the following elements;
(a) A substrate-positioning means for positioning the substrate relative to the screen mask having pattern openings;
(b) A three-dimensional measuring means for measuring an object in the range including a mounting section of the screen mask and a substrate positioning means;
(c) A moving means for moving the three-dimensional measuring means; and
(d) An origin-setting means for determining an origin position in the control program by identifying a position of a given measuring point set on an object to be measured with respect to a mechanical-coordinates-origin of the screen printing apparatus, based on a measuring result by the three dimensional measuring means.
Further another method of screen printing includes the following steps:
(a) Measuring three-dimensionally a predetermined point on the mechanism of the screen-printing apparatus by the three-dimensional measuring means having a measuring range including a screen-mask-mounting section and the substrate-positioning means for positioning the substrate with respective to the screen mask;
(b) Determining a position of predetermined measuring point set on an object with respect to a mechanical coordinate origin of the screen printing apparatus based on the three-dimensional measuring.
(c) Setting an origin of the control program.
This configuration or this method allows the apparatus to be carried out operations of adjusting mechanisms and teaching with ease and high accuracy.